U.S. patent application number 12/999337 was filed with the patent office on 2011-07-07 for composition containing (meth)acrylic polymer and copolymer having associative groups.
This patent application is currently assigned to Arkema France. Invention is credited to Nicolas Dufaure, Manuel Hidalgo, Ludwik Leibler, Francois-Genes Tournilhac.
Application Number | 20110166293 12/999337 |
Document ID | / |
Family ID | 40229908 |
Filed Date | 2011-07-07 |
United States Patent
Application |
20110166293 |
Kind Code |
A1 |
Dufaure; Nicolas ; et
al. |
July 7, 2011 |
COMPOSITION CONTAINING (METH)ACRYLIC POLYMER AND COPOLYMER HAVING
ASSOCIATIVE GROUPS
Abstract
The present invention relates to a composition containing at
least one (meth)acrylic polymer and at least one copolymer
containing motifs from at least one first monomer (A), enabling
compatibility with said (meth)acrylic polymer, and at least one
second motif (B) carrying an associative group. The invention also
relates to the use of such a copolymer having associative groups to
improve the properties of a (meth)acrylic polymer. The invention
also relates to uses of the abovementioned composition.
Inventors: |
Dufaure; Nicolas; (Bernay,
FR) ; Tournilhac; Francois-Genes; (Paris, FR)
; Hidalgo; Manuel; (Brignais, FR) ; Leibler;
Ludwik; (Paris, FR) |
Assignee: |
Arkema France
Colombes
FR
CNRS
Paris
FR
|
Family ID: |
40229908 |
Appl. No.: |
12/999337 |
Filed: |
June 12, 2009 |
PCT Filed: |
June 12, 2009 |
PCT NO: |
PCT/FR2009/051113 |
371 Date: |
February 28, 2011 |
Current U.S.
Class: |
525/69 ; 525/186;
525/207; 525/221; 525/228; 525/238; 525/55 |
Current CPC
Class: |
C08L 51/003 20130101;
C09D 151/003 20130101; C09D 151/003 20130101; C08L 2666/02
20130101; C08F 265/04 20130101; G11B 7/2533 20130101; C08L 51/003
20130101; C08L 2666/02 20130101 |
Class at
Publication: |
525/69 ; 525/55;
525/186; 525/207; 525/221; 525/228; 525/238 |
International
Class: |
C08L 79/08 20060101
C08L079/08; C08L 33/12 20060101 C08L033/12; C08L 35/00 20060101
C08L035/00; C08L 33/02 20060101 C08L033/02; C08L 33/06 20060101
C08L033/06; C08L 33/20 20060101 C08L033/20 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 17, 2008 |
FR |
0853982 |
Claims
1. A composition comprising at least one (meth)acrylic polymer and
at least one copolymer including units resulting from at least one
first monomer (A) which makes possible the compatibility with said
(meth)acrylic polymer and including at least one second unit (B)
carrying an associative group.
2. The composition as claimed in claim 1, wherein the (meth)acrylic
polymer is chosen from either poly(methyl methacrylate) or a
copolymer, one of the comonomers of which is methyl
methacrylate.
3. The composition as claimed in claim 1, wherein the (meth)acrylic
polymer represents from 10 to 99.5% by weight, with respect to the
total weight of the composition.
4. The composition as claimed in claim 1, wherein the (meth)acrylic
polymer represents from 50 to 99% by weight, with respect to the
total weight of the composition.
5. The composition as claimed in claim 1, wherein the monomer (A)
represents at least 20 mol % of the copolymer.
6. The composition as claimed in claim 1, wherein the associative
groups are chosen from imidazolidinyl, triazolyl, triazinyl,
bis-ureyl and ureido-pyrimidyl groups, preferably an imidazolidinyl
group.
7. The composition as claimed in claim 1, wherein said monomer (A)
is a monomer for which the corresponding homopolymer is known to be
miscible with the (meth)acrylic polymer or for which the presence
of units resulting from the monomer (A) results in the
compatibility with the (meth)acrylic polymer, this monomer being
chosen from: methyl methacrylate, acrylic acid, methacrylic acid,
acrylic acid esters, methacrylic acid esters, acrylonitrile and
maleic anhydride.
8. The composition as claimed in claim 1, wherein the copolymer is
capable of being obtained by grafting the associative groups to a
copolymer, already formed, comprising, in addition to the monomer
(A), a monomer (B') including at least one reactive functional
group, such as an acid, anhydride, alcohol, mercaptan, amine, epoxy
or isocyanate functional group, preferably an anhydride functional
group, by reaction of one or more modifying agents carrying, on the
one hand, an associative group and, on the other hand, a reactive
group chosen from amine, mercaptan, epoxy, isocyanate, anhydride or
alcohol groups, preferably an amine group, said reactive group
being capable of forming a covalent bond with said reactive
functional group.
9. The composition as claimed in claim 8, wherein the copolymer
including the monomer (B') is capable of being obtained by
cyclization of a copolymer of alkyl(meth)acrylate and of
(meth)acrylic acid under basic catalysis conditions.
10. The composition as claimed in claim 1, wherein the copolymer is
capable of being obtained by polymerization starting from: on the
one hand, a monomer (A) which is a (meth)acrylic monomer chosen
from: methyl methacrylate, acrylic acid, methacrylic acid, butyl
acrylate, 2-ethylhexyl acrylate, methyl acrylate, ethyl acrylate,
methoxypolyethylene glycol methacrylate, acrylonitrile and maleic
anhydride, on the other hand, a monomer (B) carrying associative
groups, preferably imidazolidinyl groups, which is advantageously
chosen from: ethylimidazolidone methacrylate and ethylimidazolidone
methacrylamide, and optionally one or more other monomers chosen
from acrylic acid or methacrylic acid, their esters, their amides
or their salts, itaconic acid, its esters, its amides or its salts,
and styrene and its derivatives.
11. The composition as claimed in claim 1, wherein the
(meth)acrylic polymer is poly(methyl methacrylate) and the
copolymer including units resulting from a monomer (A) is methyl
methacrylate.
12. A method for modifying one or more of the following properties
of a (meth)acrylic polymer: its creep strength, in particular at
more than 25.degree. C., its glass transition temperature (Tg), its
Vicat softening point, its adhesion to metal surfaces, such as
surfaces made of steel or aluminum, its elongation at break, in
particular at more than 25.degree. C., its melt strength or melt
elongational viscosity, its chemical resistance, its
processability, its surface hardness, its scratch resistance, its
thermal stability, or its resistance in stress cracking tests,
comprising the step of mixing said (meth)acrylic polymer with a
copolymer carrying associative groups as described in claim 1.
13. An item selected from the group consisting of: components or
parts of passenger compartments of motor vehicles, such as signal
lights or dashboards, in the construction and building industry,
such as windows or window frames, in decoration, such as furniture
or jewelry, in hygiene/health, such as bathtubs, wash basins or
test tubes, in domestic electrical appliances, such as microwave
oven doors or mixer bowls, in office automation and electronics,
such as portable telephone screens and optical disks (DVD, CD-ROM,
and the like), in lighting, such as globes and diffusers, in
signing, such as signs and displays, or in the cosmetics field, for
the production of bottles, wherein said item is made from the
composition as claimed in claim 1.
Description
[0001] The present invention relates to novel chemical compositions
based on (meth)acrylic polymer and on copolymer carrying
associative groups.
[0002] "Supramolecular" materials are materials composed of
compounds held together by noncovalent bonds, such as hydrogen,
ionic and/or hydrophobic bonds. They can in particular be polymers
to which associative groups are grafted, which groups are capable
of linking up via cooperative hydrogen bonds. One advantage of
these materials is that these physical bonds are reversible, in
particular under the influence of the temperature or by the action
of a selective solvent. The ease of processing and/or the
properties of the polymers, such as the mechanical, rheological,
thermal, optical, chemical or physicochemical properties, can thus
be improved by the grafting of these associative groups. The latter
can also confer the properties of polymers of high weight on
polymers of lower Weight which are easier to process.
[0003] The document U.S. Pat. No. 2,980,652 thus discloses a
product resulting from the reaction of a unit carrying
imidazolidone associative groups with a copolymer resulting from
the copolymerization of certain monomers comprising anhydride
functional groups, maleic anhydride or itaconic anhydride or
citraconic anhydride, with at least one unsaturated ethylenic
monomer. It is indicated that this product has good adhesion to
metals, glass and plastics. Example 9 discloses more particularly
the product of the reaction of N-aminoethyl-2-imidazolidone (UDETA)
with a copolymer of maleic anhydride and of methyl methacrylate.
This product is formulated in a varnish which can be sprayed over
steel panels (Examples 14 and 15).
[0004] Furthermore, the document WO 2006/016041 discloses polymers
grafted with associative groups which make it possible to confer
thereon a higher elastic modulus and a better resistance to
solvents. In this document, macromolecular chains carry associative
groups. Two main methods of preparation make it possible to obtain
such materials.
[0005] In one case, a polymer carrying reactive groups (such as
acid, epoxy or anhydride groups) is grafted with a molecule
carrying an associative group based on imidazolidone and a reactive
group (amine, alcohol, and the like). This grafting can be carried
out either by the solvent route or during a reactive extrusion
stage. This process can thus be applied only to polymers carrying
reactive functional groups.
[0006] A second route consists in introducing reactive groups
during the polymerization stage. Methacrylic monomers carrying
associative groups are used as comonomers. In comparison with the
method described above, this technique makes it possible to obtain
a broader choice of (meth)acrylic polymers carrying associative
groups. Nevertheless, the direct modification by copolymerization,
in order to be optimal, implies good control of the molecular
weights and of the molecular weight distribution, and also of the
level and distribution of associative groups in the modified
chains, which is often complicated and expensive. This type of
process also involves an extensive industrial organization, the
achievement of polymers grafted with associative groups of
different masses and different degrees of grafting involving many
grades.
[0007] In this context, the Applicant Company has been interested
in the means which make it possible to modify (meth)acrylic
polymers, such as PMMA, by supramolecular chemistry for the purpose
of improving their properties, without trying to modify all or
virtually all of the macromolecular chains of the material.
[0008] It is to the credit of the Applicant Company to have
developed a chemical composition which makes it possible to result
in a material of supramolecular type based on (meth)acrylic polymer
which exhibits improved properties while retaining a majority of
the polymer chains free from associative groups. In order to
achieve this aim, the Applicant Company has devised an "indirect
modification" of a (meth)acrylic polymer, such as PMMA, by
blending, during the processing thereof, with a copolymer rich in
monomers which, after polymerization, give blends compatible with
the (meth)acrylic polymer and further carrying associative groups.
It is thus possible to obtain a highly compatible homogeneous blend
of polymers and to indirectly convey associative groups into a
(meth)acrylic polymer for the purpose of conferring various
properties thereon.
[0009] The choice of (meth)acrylic polymers which can be modified
is thus very broad and can be made by simple blending. The user
desiring to modify such a polymer thus does not have to proceed
directly to a reactive extrusion of the polymer to be modified or
to carry out a copolymerization directly in order to obtain the
desired modification but much more simply to add, to his
(meth)acrylic polymer material to be modified, such as PMMA, a
copolymer rich in monomers which, after polymerization, give blends
compatible with the (meth)acrylic polymer and further carrying
associative groups.
[0010] More specifically, it has been demonstrated that the polymer
carrying associative groups makes it possible to confer, on the
(meth)acrylic polymer to be modified, such as PMMA, improved
properties of resistance to creep and to solvents and can
optionally contribute thereto, in addition, improved thermal
properties, in particular a higher glass transition temperature.
This can be obtained without modifying the viscoelastic behavior of
the (meth)acrylic material at the forming temperatures.
[0011] It has also been demonstrated that the content of
associative groups can be reduced, with respect to the processes
for modifying all of the chains, to obtain similar properties.
[0012] A subject matter of the present invention is thus a
composition comprising at least one (meth)acrylic polymer and at
least one copolymer including units resulting from at least one
first monomer (A) which makes possible the compatibility with said
(meth)acrylic polymer and including at least one second unit (B)
carrying an associative group.
[0013] The term "(meth)acrylic polymer" is understood to mean,
within the meaning of the invention, an acrylic polymer or a
methacrylic polymer. The (meth)acrylic polymer can in particular be
a homo- or copolymer based on methyl methacrylate. It is generally
a thermoplastic polymer. The (meth)acrylic polymer can be a
copolymer, one of the comonomers of which is methyl
methacrylate.
[0014] A preferred example of (meth)acrylic polymer is poly(methyl
methacrylate) or PMMA and its copolymers, sometimes also called
PMMA when the level of methyl methacrylate in the copolymer is
predominant. Such a polymer is sold in particular by Arkema under
the trade name Altuglas.RTM.. Other (meth)acrylic polymers which
can be used in this invention can be the poly(acrylic acid)
homopolymer, the poly(methacrylic acid) homopolymer and the
homopolymers of their esters, such as, for example, poly(butyl
acrylate), poly(2-ethylhexyl acrylate), poly(methyl acrylate),
poly(ethyl acrylate), poly(polyethylene glycol methacrylate) or
poly-(methoxypolyethylene glycol methacrylate), the
poly-(acrylonitrile) homopolymer, and also their copolymers
including at least 2 of the monomers mentioned in brackets. It is
also possible for the (meth)acrylic polymer according to the
invention to be a blend including at least 2 of the above
(meth)acrylic polymers or copolymers. The (meth)acrylic polymer
according to the invention described in this paragraph will
generally be referred to simply as (meth)acrylic polymer in that
which follows.
[0015] PMMA or its copolymers is preferred for use in the present
invention.
[0016] The (meth)acrylic polymer can be obtained according to
suspension, microsuspension, emulsion or bulk polymerization
processes well known to a person skilled in the art.
[0017] It can represent from 1 to 99.5% by weight, and preferably
from 5 to 99.5% by weight, froze 10 to 99.5% by weight, from 20 to
99.5% by weight, from 30 or from 40 to 99.5% by weight and even
from 50 to 99% by weight, with respect to the total weight of the
composition according to the invention.
[0018] This (meth)acrylic polymer can be formulated in a
composition resulting, after processing, in a final material,
preferably rigid and transparent, which can comprise one or more
additives described in more detail below.
[0019] This (meth)acrylic polymer is combined, in the composition
according to the invention, with a copolymer carrying associative
groups in order to form a "compound".
[0020] This copolymer carrying associative groups includes units of
at least one first monomer (A) which render said copolymer
compatible with said (meth)acrylic polymer and includes at least
one second unit (B) carrying an associative group. The monomer (A)
preferably represents at least 20 mol % of the copolymer. The
copolymer carrying associative groups according to the invention
will generally be referred to simply as "copolymer" in that which
follows.
[0021] The term "compatible" is understood to mean that the
(meth)acrylic polymer and the copolymer form homogeneous blend, in
the sense that they exhibit a miscibility such that the
(meth)acrylic polymer is swollen by the copolymer or that the
(meth)acrylic polymer swells the copolymer, in the proportions used
in the blend. This is reflected in that the (meth)acrylic polymer
and the copolymer form only a single phase. Depending on the nature
of the copolymer and in particular on the monomer (A) used for the
synthesis thereof, the compatibility within the meaning of the
invention with the (meth)acrylic polymer can be obtained in
variable proportions of the blend of the two polymers,
((meth)acrylic polymer and copolymer carrying associative groups).
This compatibility can be demonstrated by physical measurements of
miscibility.
[0022] This miscibility can be pinpointed by various analytical
methods known to a person skilled in the art, such as scanning
electron microscopy (SEM), transmission electron microscopy (TEM)
or atomic force microscopy (AFM), often making it possible to
locate inhomogeneities of the blends in the form of domains with a
characteristic size of greater than 1 micron (immiscibility), and
by measurements of the glass transition temperature Tg of the blend
of the two polymers the miscibility is then reflected by the
existence of a single Tg for the blend. The methods for measuring
the Tg of the polymers and of the blends of polymers are known to a
person skilled in the art and include differential scanning
calorimetry (DSC), volumetric analysis or dynamic mechanical
analysis (DMA). It is also possible to determine the miscibility by
optical measurements, such as the transparency. When the
miscibility is determined by transparency measurements in
noncrystalline polymer systems, such as PMMA, the difference in
transparency between that of a test specimen or sheet of the blend,
with a thickness of 2 to 4 mm, and the transparency of a test
specimen or sheet of the blend of the (meth)acrylic polymer alone
and with the same thickness, should not be perceptible to the naked
eye; in other words, when the blend is not compatible within the
meaning of the invention, there appears, in comparison with the
sample of the (meth)acrylic polymer alone, a veil or an opacity
sufficiently perceptible to the eye and easily quantifiable by
optical transparency measurements known to a person skilled in the
art (such as the percentage of transmission or the percentage of
haze).
[0023] Thus, any copolymer carrying associative groups and which is
compatible, within the meaning explained above, with the
(meth)acrylic polymer can be used for the invention, in particular
any copolymer based on a monomer (A) for which the corresponding
homopolymer is known to be miscible with the (meth)acrylic polymer
or for which the presence of units resulting from the monomer (A)
results in the compatibility with the (meth)acrylic polymer.
[0024] The choice of the monomer (A) of the copolymer carrying
associative groups depends on the composition of the (meth)acrylic
polymer according to the invention.
[0025] According to the invention, it is thus possible to blend a
(meth)acrylic polymer with a copolymer carrying associative groups
of very different molecular weight, such that they combine the
advantages of these two types of polymers.
[0026] According to the invention, it is thus possible to blend a
(meth)acrylic polymer (polymer 1) with a copolymer carrying
associative groups (polymer 2) of very different molecular weight,
such as to combine the advantages of these two types of polymers.
More particularly, if polymer 1 of weight W1 is blended with a low
proportion of polymer 2 of molecular weight W2, with W2>W1, it
is possible to obtain a material having a viscosity at low gradient
which is substantially higher than that of polymer 1, whereas the
viscosity at high gradient remains not much greater than that of
polymer 1.
[0027] This situation is advantageous from the viewpoint of the
processes for processing plastics when it is desired to obtain both
a relatively low viscosity at the forming velocities and a high
melt strength.
[0028] This method also makes it possible to have improved
properties of impact strength and of resistance to solvents by
using relatively low contents of copolymer carrying associative
groups (polymer 2).
[0029] Mention may be made, as nonexclusive examples of monomers
(A), of methyl methacrylate, acrylic acid, methacrylic acid,
acrylic acid esters, methacrylic acid esters, acrylonitrile or
maleic anhydride. Mention may be made, as examples of copolymers
carrying associative groups which can be blended, at variable
proportions according to their nature and that of the (meth)acrylic
polymer, with the (meth)acrylic polymer in order to obtain the
compatibility and the "indirect modification" effects via
reversible physical bonds according to the invention, of methyl
methacrylate copolymers (referred to as copolymers of PMMA type)
carrying associative groups, maleic anhydride copolymers carrying
associative groups or acrylonitrile copolymers carrying associative
groups, and more generally of all the polymers resulting from the
abovementioned monomers.
[0030] The term "associative groups" is understood to mean groups
capable of associating with one another via hydrogen bonds,
advantageously via 1 to 6 hydrogen bonds. Examples of associative
groups which can be used according to the invention are the
imidazolidinyl, triazolyl, triazinyl, bis-ureyl or ureido-pyrimidyl
groups, the imidazolidinyl groups being preferred.
[0031] According to one embodiment of the invention, the
associative groups can be introduced during the formation of the
copolymer. This embodiment is not limiting, it also being possible
to envisage a reactive extrusion of a blend of associative groups
with the preformed (meth)acrylic polymer.
[0032] The copolymer is thus capable of being obtained by
copolymerization of the monomer (A) with a monomer (B) Which
carries associative groups and optionally one or more other
monomers, preferably starting from: [0033] on the one hand, a
monomer (A) which is a monomer for which the corresponding
homopolymer is known to be miscible with the (meth)acrylic polymer
or for which the presence of units resulting from the monomer (A)
results in the compatibility with the (meth)acrylic polymer, this
monomer being chosen from: methyl methacrylate, acrylic acid,
methacrylic acid, acrylic acid esters, methacrylic acid esters,
acrylonitrile and maleic anhydride, [0034] on the other hand, a
monomer (B) carrying associative groups, preferably imidazolidinyl
groups, which is advantageously chosen from: ethylimidazolidone
methacrylate (or EIOM) and ethylimidazolidone methacrylamide,
[0035] optionally one or more other monomers chosen from acrylic
acid or methacrylic acid, their esters, their amides or their
salts, itaconic acid, its esters, its amides or its salts, styrene
and its derivatives, such as 4-styrenesulfonate.
[0036] In a preferred embodiment of the composition, the
(meth)acrylic polymer is poly(methyl methacrylate) and the
copolymer including units resulting from a monomer (A) is methyl
methacrylate. Thus, the composition can comprise a blend of PMMA
and of PMMA carrying associative groups.
[0037] Such a copolymer can be prepared according to known methods
of radical polymerization in solution in solvents, such as
chloroform or tetrahydrofuran, or in dispersed medium, such as, in
particular, in aqueous suspension or emulsion. Preferably, the
copolymer used in the invention can be obtained by radical
polymerization in aqueous suspension or emulsion. In the case of
polymerizations in solution or in aqueous suspension, the
polymerization can be initiated using initiators of radical
polymerization which are soluble in the mixture of monomers.
Different mechanisms for generating radicals can be employed, such
as, for example, thermal decomposition, oxidation/reduction
reactions or the decomposition brought about by electromagnetic
radiation and in particular the light in the ultraviolet region.
Nonexclusive examples of initiators include hydroperoxides,
dialkylperoxides, diacylperoxides, peroxy esters,
peroxydicarbonates, peroxyacetals, azo compounds and their
combinations with agents which promote their decomposition, such as
amines and metal atoms.
[0038] Mention may be made, as examples of hydroperoxides, of
tert-butyl hydroperoxide, tert-amyl hydroperoxide, cumyl
hydroperoxide, 2,5-dimethyl-2,5-di(hydroperoxy)-hexane,
diisopropylbenzene monohydroperoxide and para-menthane
hydroperoxide.
[0039] Mention may be made, as examples of dialkyl peroxides, of
2,5-dimethyl-2,5-di(tert-butylperoxy)hex-3-yne,
di-(tert-butyl)peroxide, di(tert-amyl)peroxide,
1,3-di(tert-butylperoxyisopropyl)benzene,
2,5dimethyl-2,5-di(tert-butylperoxy)hexyne,
1,1,4,4,7,7-hexamethyl-cyclo-4,7-diperoxynonane or
3,3,6,6,9,9-hexamethyl-cyclo-1,2,4,5-tetraoxanonane.
[0040] Mention may be made, as examples of diacyl peroxides, of
benzoyl peroxide, lauroyl peroxide decanoyl peroxide,
3,5,5-trimethylhexanoyl peroxide or acetyl cyclohexylsulfonyl
peroxide.
[0041] Mention may be made, as examples of peroxy esters, of
tert-butyl peroxybenzoate, tert-butyl peroxyacetate, tent-butyl
peroxy-3,5,5-trimethylhexanoate, tert-amyl
peroxy-3,5,5-trimethylhexanoate,
2,5-dimethyl-2,5-di-(benzoylperoxy)hexane OO-tert-butyl O-isopropyl
mono-peroxycarbonate, OO-tert-butyl O-(2-ethylhexyl)
mono-peroxycarbonate, tert-butyl peroxyisobutyrate tert-butyl
peroxy-2-ethylhexanoate, tert-amyl peroxy-2-ethylhexanoate,
2,5-dimethyl-2,5-di(2-ethylhexanoyl-peroxy)hexane, tert-butyl
peroxyneodecanoate, tert-butyl peroxyisononanoate, tert-butyl
peroxypivalate, tert-amyl peroxypivalate, .alpha.-cumyl
peroxyneodecanoate, tert-amyl peroxydecanoate, tert-butyl
3-hydroxy-1,1-dimethylbutylperoxyneodecanoate and tert-butyl
peroxymaleate.
[0042] Mention may be made, as examples of peroxydicarbonates, of
di(2-ethylhexyl) peroxydicarbonate, dicyclohexyl peroxydicarbonate,
di(n-propyl) peroxydicarbonate or
di(4-(tert-butyl)cyclohexyl)peroxydicarbonate.
[0043] Mention may be made, as examples of peroxyacetals, of
1,1-di(tert-butylperoxy)cyclohexane,
1,1,-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, ethyl
3,3-di(tert-butylperoxy)butyrate, ethyl
3,3-di(tert-amyl-peroxy)butyrate, n-butyl
4,4-di(tert-butylperoxy)-valerate, 2,2-di(tert-butylperoxy)butane,
1,1-di(tert-amylperoxy)cyclohexane or
2,2-bis[4,4-di(tert-butyl-peroxy)cyclohexyl]propane.
[0044] Mention may be made, as examples of azo compounds, of
2,2'-azobisisobutyronitrile or
2-[(E)-(1-cyano-1-methylethyl)diazenyl]-2-methylpropanenitrile,
2-[(E)-(1-cyano-1-methylpropyl)diazenyl]-2-methylbutanenitrile or
azobismethylbutyronitrile, azobisisobutyramide, dimethyl
azobisdiisobutyrate, diethyl azobisisobutyrate, or cyanovaleric
acid or
4-[(E)-(3-carboxy-1-cyano-1-methylpropyl)diazenyl-4-cyanopentanoic
acid.
[0045] The polymerization can also be initiated with
initiators/controllers of controlled radical polymerization such as
alkoxyamines, and more particularly with
2-methyl-2-[N-(tert-butyl)-N-(1-diethoxyphoshoryl-2,2-dimethylpropyl)amin-
oxy]propionic acid of following formula:
##STR00001##
[0046] sold, by Arkema under the BlocBuilder.RTM. brand, and its
metal or organic salts.
[0047] These initiators can be used at a level of 0.05 to 10% by
weight, with respect to the total weight of the monomers.
[0048] In the case of the polymerizations in organic solution or in
aqueous suspension or emulsion, in addition to the polymerization
initiators, it may prove to be of use to dissolve other additives
in the monomers, among which additives may be mentioned
chain-transfer agents which make it possible to reduce the
molecular weights. Mention may be made, as examples of
chain-transfer agents, of alkyl mercaptans, such as methyl
mercaptan, ethyl mercaptan, n-propyl mercaptan, isopropyl
mercaptan, n-butyl mercaptan, tert-butyl mercaptan, cyclohexyl
mercaptan, benzyl mercaptan, n-octyl mercaptan, tert-nonyl
mercaptan, n-dodecyl mercaptan or tert-dodecyl mercaptan, or alkyl
thioglycolates, such as methyl thioglycolate, ethyl thioglycolate,
2-ethylhexyl thioglycolate or isooctyl thioglycolate. The
chain-transfer agents are used in proportions of between 0.01 and
10% by weight and preferably between 0.5 and 2% by weight, with
respect to the total weight of the monomers.
[0049] In the case of the polymerizations in organic solution or in
a dispersed medium, such as aqueous suspension or emulsion
polymerization, it is also possible to dissolve other additives in
the monomers, such as antioxidants, for example butylated
hydroxytoluene BHT, biocides or activators of polymerization
initiators. These additives are used in proportions of between 0.01
and 5% by weight, with respect to the total weight of the
monomers.
[0050] In the case of the polymerizations in aqueous suspension,
the mixture of the monomers comprising the polymerization initiator
and optionally other additives dissolved in this mixture is
dispersed in a continuous aqueous phase comprising a suspending
agent which promotes the stability of the suspension during the
polymerization. Mention may be made, among suspending agents which
can be used, as nonexclusive example, of finely divided mineral
powders, such as talc or calcium triphosphate, polymers which are
suspending agents, sometimes also known as protective colloids,
such as partially or completely hydrolyzed polyvinyl alcohols,
copolymers of styrene and of (meth)acrylic acid, with or without a
third monomer, such as .alpha.-methylstyrene, some surfactants,
such as sorbitan ethoxylated esters, thickening water-soluble
polymers, such as hydroxyethylcellulose, polymers and copolymers
based on (meth)acrylic acid or its salts, polymers and copolymers
based on (meth)acrylamide and its derivatives, or
polyacrylamidopropanesulfonate. The suspending agents are used in
proportions ranging from 0.05 to 10% by weight and preferably from
0.1 to 5% by weight, with respect to the total weight of the
dispersed phase comprising the monomers. In combination with the
suspending agents, other additives added to the aqueous phase, such
as salts, for example sodium sulfate or ammonium sulfate, sometimes
known as "extenders", which make it possible to control the ionic
strength of the medium, or pH regulators, such as sodium
bicarbonate, can be used in proportions ranging from 0.05 to 5% by
weight, with respect to the total weight of the continuous aqueous
phase.
[0051] In the case of the polymerizations in an aqueous emulsion,
water-soluble radical polymerization initiators are used. Different
mechanisms for generating radicals can be employed such as, for
example, thermal decomposition, oxidation/reduction reactions or
the decomposition brought about by electromagnetic radiation and in
particular the light in the ultraviolet region. Nonexclusive
examples of water-soluble initiators include hydroperoxides, such
as tert-butyl hydroperoxide, water-soluble azo compounds, such as
2,2'-azobis(2-amidinopropane)dihydrochloride and organic or
inorganic salts of 4,4'-azobis(4-cyanovaleric acid), or inorganic
oxidizing agents, such as sodium persulfate, potassium persulfate
or ammonium persulfate, aqueous hydrogen peroxide solution,
perchlorates, percarbonates or ferric salts; these oxidizing agents
can be used alone or in combination with inorganic or organic
reducing agents, such as sodium bisulfite, sodium metabisulfite,
potassium bisulfite or potassium metabisulfite, vitamin C, or
sodium hypophosphite or potassium hypophosphite. These organic or
inorganic reducing agents can also be used alone, that is to say in
the absence of inorganic oxidizing agents. These initiators which
are soluble in the aqueous phase are used in the case of the
emulsion polymerizations in proportions ranging from 0.01 to 10% by
weight, with respect to the total weight of the monomers.
[0052] In the case of the polymerizations in aqueous emulsion,
surfactants or stabilizers which make it possible to form the
starting emulsions and to stabilize the final latexes obtained can
be used. Three families of surfactants or stabilizers can be
considered, namely: [0053] 1) surface-active molecules of natural
or synthetic origin having a dispersing and stabilizing effect by
electrostatic repulsion and comprising amphiphilic molecules which
are positively or negatively charged, or which form zwitterions
(amphoteric), in the aqueous phase, among which may be mentioned,
as nonexclusive examples: sodium or potassium alkyl sulfates or
alkylsulfonates, in particular sodium dodecyl sulfate, sodium or
potassium alkylaryl sulfates or alkylarylsulfonates, in particular
sodium dodecylbenzenesulfonate, potassium, sodium or ammonium salts
of fatty acids, in particular sodium stearate, alkylated and
disulfonated diphenyl oxides, in particular the commercial
surfactants of the Dowfax.RTM. range, such as Dowfax.RTM. 2A1,
sulfosuccinates and in particular the commercial surfactant's of
the Aerosol.RTM. range, such as Aerosol.RTM. MA 80, which is sodium
dihexyl sulfosuccinate, or Aerosol.RTM. OT-75, which is dioctyl
sodium sulfosuccinate, phosphoric esters, fatty amines, polyamines
and their salts, quaternary ammonium salts, such as
alkyltrimethylammonium chlorides or bromides, betaines, such as
N-alkyl betaines or sulfobetaines, imidazoline carboxylates, and
the ethoxylated derivatives of all these compounds, [0054] 2)
uncharged or nonionic surface-active molecules having dispersing
and stabilizing effect by steric repulsion, among which may be
mentioned, as nonexclusive examples: ethoxylated alkylphenols,
ethoxylated fatty alcohols, polyethylene oxide and polypropylene
oxide block copolymers, such as those of the Pluronics range, fatty
acid esters or alkyl polyglycosides, [0055] 3) charged or uncharged
amphiphilic or completely hydrophilic polymeric molecules, among
which may be mentioned, as nonexclusive examples: water-soluble
polymers of natural or synthetic origin, such as polymers and
copolymers of (meth)acrylic acid and their salts, polymers and
copolymers of acrylamide and its derivatives, polymers based on
vinyl alcohol and vinyl acetate, hydroxyethylcellulose and
hydrophobically modified hydroxyethylcellulose,
polyvinylcaprolactam or polyvinylpyrrolidone.
[0056] These dispersants or stabilizers used in emulsion
polymerization are present at a level of 0.1 to 10% by weight, with
respect to the total weight of the monomers. It is also possible to
carry out emulsion polymerizations in the absence of surfactants or
stabilizing or dispersing agents; in this specific case, the final
proportions of polymer, expressed in terms of final solids content
or final dry extract, that is to say after evaporation of the
volatiles and in particular of the water, are less than 20% by
weight of the total of the latex resulting from the emulsion
polymerization.
[0057] The solution processes, on the one hand, and the aqueous
suspension or emulsion processes, on the other hand, which can be
used for the synthesis of the copolymers carrying the associative
groups according to the invention can be carried out at atmospheric
pressure or under pressure and at polymerization temperatures of
between 5.degree. C. and 180.degree. C. Preferably, the copolymer
is obtained by an aqueous suspension or emulsion process at
atmospheric pressure and polymerization temperatures of between 50
and 95.degree. C. The final concentrations or concentrations after
polymerization of polymer and other nonvolatile components for the
polymerizations in a solution, aqueous suspension or aqueous
emulsion are between 1 and 75% by weight and preferably between 15
and 50% by weight, expressed as final dry extract or final solids
content, with respect to the total weight of the solution,
suspension or emulsion (latex).
[0058] The process for the synthesis of the copolymer can be
continuous or batchwise or of semicontinuous type, that is to say
with metered additions of components, such as, for example, metered
additions of monomers, as is or preemulsified, as is often the case
in aqueous emulsion polymerizations, or metered additions of
additives, such as dispersants or stabilizers, initiators or other
additives.
[0059] Generally, the preferred aqueous suspension and aqueous
emulsion processes used to obtain the copolymer carrying the
associative groups according to the invention are well known to a
person skilled in the art and are described in general and
specialist works, such as, for example, in Chapter 7 of the book
Les latex synthetiques: Elaboration, Proprietes, Applications
[Synthetic Latexes: Preparation, Properties and Applications],
edited by C. Pichot and J. C. Daniel (Editions TEC&DOC of
Lavoisier, France, 2006).
[0060] In another embodiment of the invention, the copolymer can be
obtained by grafting the associative groups to a copolymer, already
formed, comprising, in addition to the monomer (A), a monomer (B')
including at least one reactive functional group, such as an acid,
anhydride, alcohol, mercaptan, amine, epoxy or isocyanate
functional group, preferably an anhydride functional group, by
reaction of one or more modifying agents carrying, on the one,
hand, an associative group and, on the other hand, a reactive group
chosen from amine, mercaptan, epoxy, isocyanate, anhydride or
alcohol groups, preferably an amine group, said reactive group
being capable of forming a covalent bond with said reactive
functional group.
[0061] In this embodiment, the copolymer carrying reactive
functional groups can, for example, be an alkyl (meth)acrylate
homo- or copolymer, for example having a number-average molecular
weight ranging from 1000 to 10 090 000 g/mol and preferably from
5000 to 100 000 g/mol, including anhydride functional groups. This
copolymer can be obtained from a copolymer of alkyl(meth)acrylate,
in particular methyl(meth)acrylate, and of (meth)acrylic acid, such
as the Altuglas.RTM. HT 121 grade from Arkema, for example
including between 1 and 15 mol % of (meth)acrylic acid units,
according to a cyclization process, under basic catalysis
conditions, which can in particular be carried out in an extruder.
The preferred basic Catalysts include sodium hydroxide and sodium
methoxide, CH.sub.3ONa. The cyclization can be carried out by
passing the starting copolymer with the catalyst and optionally
other additives, such as lubricants, antioxidants, dyes or optical
correctors, to give gloss and reduce yellowing, through a single-
or twin-screw extruder; the extrusion temperature can be between
200 and 300.degree. C. and preferably greater than 250.degree. C.
One or more extrusion passes can be carried out in order to obtain
the desired level of cyclization (formation of glutaric anhydride).
The degree of cyclization can be controlled in order to adjust the
level of anhydride functional groups obtained, which can, for
example, range from 0.1 to 20 mol %.
[0062] The reactive and associative groups respectively of the
modifying agent can be separated by a rigid or flexible chain
composed of 1 to 30 carbon atoms, some at least of which can be
substituted, and optionally of one or More heteroatoms chosen in
particular from sulfur, oxygen and nitrogen, said chain optionally
including one or more ester or amide bridges. It is preferably a
linear or branched C.sub.1-C.sub.10 alkylene chain optionally
interrupted by one or more nitrogen atoms, more preferably a linear
C.sub.1-C.sub.6 alkylene chain.
[0063] Preferred examples of modifying agents are
1-(2-aminoethyl)imidazolidin-2-one (UDETA),
1-(2-[(2-aminoethyl)amino]ethyl)imidazolidone (UTETA),
1-(2-{2-[(2-aminoethylamino)]ethylamino}ethyl)imidazolidone
(UTEPA), 3-amino-1H-1,2,4-triazole (3-ATA) and
4-amino-1H-1,2,4-triazole (4-ATA). UDETA is preferred for use in
the present invention.
[0064] The amines carrying imidazolidone functional groups can
themselves result from the reaction of urea with at least one
compound chosen from alkyleneamines and amines. Thus, UDETA can be
prepared by reacting urea with diethylenetriamine (DETA).
[0065] The number of associative groups carried by the copolymer in
this embodiment according to the invention can be simply adjusted
by varying the amount of modifying agent or the reaction time and
reaction temperature. It is generally preferable for the amount of
modifying agent to represent from 0.5 to 15% by weight, more
preferably from 1 to 5% by weight, with respect to the weight of
the copolymer carrying reactive functional groups, and/or for the
mean number of associative groups per copolymer chain to be between
1 and 200 and preferably between 1 and 30.
[0066] The grafting process is carried out by reacting the
modifying agent and the copolymer carrying reactive functional
groups. This stage can be carried out in the molten state, for
example in an extruder or an internal mixer, at a temperature which
can range from 150 to 300.degree. C. and preferably from 200 to
280.degree. C. The modifying agent is blended with the polymer,
alone or using an additive which makes possible the impregnation of
the solid polymer grains with the premelted modifying agent. The
solid blend, before introduction into the extruder or the mixer,
can be rendered more homogeneous by cooling in order to cause the
modifying agent to solidify. It is also possible to meter the
latter into the extruder or the mixer after the polymer to be
grafted has started melting. The time at the grafting temperature
can range from a few seconds to 5 minutes. The modifying agent can
be introduced into the extruder in the form of a masterbatch in a
polymer which can be the polymer to be grafted. According to this
method of introduction, the masterbatch can comprise up to 30% by
weight of the modifying agent; subsequently, the masterbatch is
"diluted" in the polymer to be grafted during the grafting
operation. According to another possibility, the grafting can be
carried out by reaction in a solvent phase, for example in
anhydrous chloroform. In this base, the reaction temperature can
range from 5 to 75.degree. C., for times ranging from a few minutes
to a day, and at concentrations of polymer before grafting of
between 1 and 50% by weight, with respect to the total weight of
the solution.
[0067] The copolymer carrying associative groups obtained according
to one or other of the above embodiments can be provided in
particular in the form of granules or of a powder. It is blended
with the (meth)acrylic polymer described above by any means, in
particular by calendaring, extrusion, melt blending in a mixing
chamber, pressing, injection molding or dissolution in a common
solvent, followed by separation of the solvent.
[0068] The level of copolymer carrying associative groups
represents, for example, from 0.1 to 75% by weight of this blend,
for example from 1 to 40% by weight in the case of PMMA.
[0069] It has been demonstrated that this copolymer makes it
possible to improve some mechanical and chemical properties of the
(meth)acrylic polymer with which it is blended.
[0070] Another subject matter of the present invention is thus the
use of a copolymer carrying associative groups as is described
above for improving one or more of the following properties of a
(meth)acrylic polymer: its creep strength, in particular at more
than 25.degree. C., its glass transition temperature (Tg), its
Vicat softening point, its adhesion to metal surfaces, such as
surfaces made Of steel or aluminum, its elongation at break, in
particular at more than 25.degree. C., its melt strength or melt
elongational viscosity, its chemical resistance, its
processability, its surface hardness, its scratch resistance or its
resistance in stress cracking tests.
[0071] Stress cracking is a term used to describe a phenomenon of
chemical attack of a product which acts on polymeric material in a
way which is scarcely perceptible when this material is not
subjected to mechanical stress. However, contact of the material
With the product brings about the formation microcracks. When the
material is then placed under stress, propagation of the
microcracks occurs, resulting in embrittlement of the material and
in failure of the latter.
[0072] Apart from the copolymer carrying the associative groups
according to the invention, the composition according to the
invention can additionally include various additives, including
[0073] lubricants, such as stearic acid, palmitic acid or stearyl
alcohol, [0074] dyes, [0075] inorganic or organic pigments, such as
those described in the document "Plastics Additives and Modifiers
Handbook, Section VIII, Colorants", J. Edenbaum, Ed., Van Nostrand,
pages 884-954. Mention may be made, as examples of pigments which
can be used, of carbon black, titanium dioxide, clay, metal
particles or treated mica particles of the Iriodin.RTM. brand sold
by Merck, [0076] heat stabilizers, such as tert-dodecyl disulfide
(DtDDS), Irganox 1076 or Tinuvin P, [0077] UV stabilizers, such as
those described in the document "Plastics Additives and Modifiers
Handbook, Chap. 16, Environmental Protective Agents", J. Edenbaum,
Ed., Van Nostrand, pages 208-271. Preferably, the UV stabilizer is
a compound of the family of the HALS, triazines, benzotriazoles or
benzophenones. Use may be made of combinations of several UV
stabilizers in order to obtain a better resistance to UV radiation,
[0078] costabilizers, [0079] antioxidants, for example hindered
phenols, such as the compounds Irganox 1010 and 1098 from Ciba,
phosphites and HALS, [0080] fillers or reinforcements, in
particular cellulose fillers, talc, calcium carbonate mica or
wollastonite, glass or metal oxides or hydrates, [0081] antistatic
agents such as amine derivatives and phosphoric esters, [0082]
fungicides and biocides, [0083] impact modifiers, such as MBS
copolymers, including Clearstrength.RTM. from Arkema, and acrylic
modifiers of core-shell type, such as the Durastrength.RTM.
products from Arkema, and also those described in international
application WO 06/053984, [0084] flame retardants, including
antimony trioxide, zinc borate and brominated or chlorinated
phosphate esters, and those described in patent application EP 1
777 257, [0085] flattening agents, which can be inorganic fillers,
such as, for example, talc, calcium carbonate, titanium dioxide or
zinc oxide, or inorganic fillers, such as, for example, crosslinked
beads based on styrene and/or MMA (examples of such beads are given
in EP 1 174 465), [0086] solvents, and [0087] their mixtures.
[0088] These additives can, for example, represent from 0.1 to 50%
of the total weight of the composition.
[0089] In addition to the solid form, this composition can be
provided in particular in the form of emulsions, of suspensions or
of solutions.
[0090] The composition according to the invention can be used to
manufacture components used in the motor vehicle industry, such as
signal lights or dashboards, in the construction and building
industry, such as windows or window frames, in decoration, such as
furniture or jewelry, in hygiene/health, such as bathtubs, wash
basins or test tubes, in domestic electrical appliances, such as
microwave oven doors or mixer bowls, in office automation and
electronics, such as portable telephone screens and optical disks
(DVD, CD-ROM, and the like), in lighting, such globes and
diffusers, in signing, such as signs and displays, or in the
cosmetics field, for the production of bottles.
[0091] Another subject matter of the invention is thus the
abovementioned uses.
[0092] This composition can be formed by calendering, extrusion,
extrusion-blow molding, injection molding, rotational molding,
thermoforming, and the like.
BRIEF DESCRIPTION OF THE DRAWINGS
[0093] A better understanding of the invention will be obtained in
the light of the following examples, given solely for illustrative
purposes, and by reference to the appended figures, in which:
[0094] FIG. 1 represents the complex viscosity of the polymers
V825T and HT121 and of two compositions formed of a blend of PMMA
and PMMA copolymer carrying associative groups or of PMMA and PMMA
copolymer without associative groups, in 90/10 ratios,
[0095] FIG. 2 represents the complex viscosity of the polymers
V825T and HT121 and of two compositions formed of a blend of PMMA
and PMMA copolymer carrying associative groups or of PMMA and PMMA
copolymer without associative groups, in 75/25 ratios.
[0096] FIG. 3 represents the strain in a creep test at 100.degree.
C. under a stress of 10 MPa for compositions formed of a blend of
PMMA and PMMA copolymer carrying associative groups or of PMMA and
PMMA copolymer without associative groups, and also for the polymer
V825T.
[0097] FIG. 4 represents the change in the normalized stress during
the stress cracking test for the compositions formed of a blend of
PMMA and PMMA copolymer carrying associative groups or of PMMA and
PMMA copolymer without associative groups, and also for the polymer
V825T.
EXAMPLES
Example 1
Preparation of a Copolymer According to the Invention by Grafting
of Associative Groups
[0098] A modifying agent, namely UDETA carrying an imidazolidinyl
associative group and an amine reactive group, was grafted to a
copolymer of methyl methacrylate, of methacrylic acid and of
glutaric anhydride. This copolymer is itself obtained by partial
cyclization of a copolymer of methyl methacrylate and of
methacrylic acid. The cyclization reaction can be carried out in
the molten state in an extruder or any other appropriate mixer with
optionally the help of a basic catalyst, such as sodium hydroxide.
This reaction can also be carried out in an oven under high vacuum.
The grafting reaction on the copolymer carrying the glutaric
anhydride functional groups can subsequently be carried out either
in the molten state, in an extruder or any other appropriate mixer,
or in solution in an appropriate solvent, such as chloroform.
[0099] Specifically, a copolymer of methyl methacrylate and of
methacrylic acid sold by Arkema under the name Altuglas.RTM. HT121
(copolymer comprising approximately 5% by weight of methacrylic
acid comonomer) was partially cyclized by placing it in an oven
under vacuum at 235.degree. C. for 24 hours. The acid groups of the
starting copolymer have a tendency to cyclize to more than 90% by
reaction either with a neighboring, acid group (departure of water)
or with a neighboring methyl ester group (departure of methanol).
The copolymer thus obtained is subsequently grafted with UDETA by
extrusion of the cyclized copolymer as a blend with UDETA in a DSM
twin-screw microextruder equipped with a recirculation pipe and
with a capacity of 15 g. The rotational speed of the screws is set
at 200 revolutions per minute and the temperature at 230.degree.
C.; flushing with nitrogen makes it possible to prevent the
materials from decomposing. The UDETA is introduced in a proportion
of 4.5% by weight, with respect to the copolymer/UDETA combination.
The residence time of the polymer/UDETA blend in the microextruder
is set at 5 minutes. This modified polymer is denoted hereinbelow
by "HT121g".
Example 2
Preparation of Compositions According to the Invention
[0100] The sample HT121g obtained in Example 1 and the product
HT121 were each blended in a proportion of 10% and 20% by weight
with the same PMMA (sold by Arkema under the name Altuglas.RTM.
V825T). The blends are produced in the same microextruder as that
mentioned in Example 1, at a temperature of 230.degree. C., while
flushing with nitrogen and for 5 minutes. The stirring speed is
adjusted to 200 revolutions per minute.
[0101] The 4 formulations obtained are summarized in Table 1.
TABLE-US-00001 TABLE 1 Percentages by Tg weight V825T HT121 HT121g
(.degree. C.) Composition 1 90 10 117 Composition 2 75 25 118.5
Composition g1 90 10 118 Composition g2 75 25 117.5
[0102] This table also exhibits the Tg values of the blends
measured by DSC at 10.degree. C./min using a DSC Q1000 from TA
Instruments operating in the T4 mode. For each blend, just one Tg
can be identified. The Tg values of V825T, HT121 and HT121g were
measured under the same conditions respectively at 114.5, 122 and
122.degree. C. The Tg values of the blends, which are sole values
and between the Tg values of the 2 materials constituting the
blend, indicate that the blends are highly miscible.
Example 3
Rheological Measurements
[0103] Compositions 1, 2, g1 and g2, and the polymers V825T and
HT121, were subjected to rheological measurements at 160.degree. C.
An Ares rheometer from Rheometric Scientific, equipped with
parallel plates with a diameter of 25 mm, was used. The samples
were dried at 105.degree. C. under vacuum for 16 hours before the
test in order to prevent the formation of bubbles during the
experiments. Frequency sweeps were carried out between 100 and 0.01
rad/s, the strains being sufficiently low to remain within the
linear domain. The modulus of the complex viscosity for the 6
products studied is represented in FIGS. 1 and 2.
[0104] It is observed that the addition of the PMMA copolymer
carrying associative groups is not reflected by an increase in
viscosity with respect to V825T. Compositions g1 and g2 will thus
have a forming very comparable to that of V825T.
Example 4
Creep Tests
[0105] Compositions 1, 2, g1 and g2 and the polymer V825T were
subjected to a creep test at 100.degree. C.
[0106] 4A Protocol
[0107] The test consists in imposing a constant stress, in
cantilever bending, on the test material and in measuring the
change in the resulting strain over time. For a given stress, the
greater the creep strength of the material, the lower the strain
over time. The sample is composed of the central part of a tensile
test specimen, injected using a DACA microinjector operating with a
hold pressure of 12 bar. The temperatures of the barrel and of the
mold were respectively set at 285.degree. C. and 110.degree. C. The
sample is a parallelepiped with a length of 25 mm, a width of 4 mm
and a thickness of 1.5 mm. The test is carried out using a DMA 2980
from TA Instruments equipped with Cantilever bending geometry. The
temperature is set at 100.degree. C. and, after leaving the sample
in the oven for 5 minutes in order to equilibrate the temperature,
a stress of 10 MPa is applied for 3 hours. The resulting strain of
the sample is measured over time.
[0108] 4B Results
[0109] As illustrated in FIG. 3, Compositions g1 and g2, including
the copolymer carrying associative groups according to the
invention, exhibit a better creep strength than the PMMA V825T
alone. The creep curves for Compositions 1 and 2 prove that this
effect is not due to the HT121; on the contrary, the latter
ungrafted polymer results in a deterioration in the creep strength
properties.
Example 5
Stress Cracking Tests
[0110] Compositions 1, 2, g1 and g2 and the polymer V825T were
subjected to a stress cracking test at ambient temperature.
[0111] 5A Protocol
[0112] The stress cracking test combines the action of solvent and
of a stress. This is an important test for polymer materials as a
large part of the defects observed during the use of these
materials is due to this two-fold stress-solvent action. More
specifically, the test carried out consists in imposing, in the
presence of a solvent, a constant strain in three-point bending on
the test material. The times for failure of the sample or for the
appearance of cracks are measured. The change in the stress during
the test can also be recorded. The deterioration of the sample is
represented by these failure/crack phenomena and by the speed of
the fall in stress during the test. The most resistant products are
thus those with the longest decomposition times or with the greater
stability of the stress during the test. The sample is prepared
according to the same procedure as that described in Example 4. The
test is carried out using an item of equipment designed in the
laboratory: a controlled strain Ares rheometer provided with a
normal force sensor is equipped with three-point bending geometry,
where the length of the sample between the two extreme points is
24.25 mm. The strain is set at 1.6% using the displacement control
of the rheometer and the stress is calculated from the normal force
recorded by the rheometer. A plastic pipe conveys, from a syringe
mounted on a syringe driver, the solvent to be deposited on the
surface of the sample. As soon as the desired strain is reached, a
drop of solvent (mixture of equal weights of water and ethanol) is
deposited on the sample. A droplet is subsequently deposited every
two minutes in order to compensate for the losses due to
evaporation. A camera connected to a computer makes it possible to
record the change in the surface appearance of the sample over
time.
[0113] 5B Results
[0114] It is observed, in particular in FIG. 4, that the relaxation
of the stresses is lower for the blends with HT121g1 and that the
cracks are much fewer for these same compositions, with respect to
the reference product V825T. It may thus be concluded that
Composition g1 exhibits a better stress cracking resistance than
V825T and than Composition 1, and Composition g2 also exhibits a
better resistance than V825T and than Composition 2. The
compositions including the copolymer carrying associative groups
according to the invention thus exhibit a better resistance to the
combined action of a solvent and of a stress than the PMMA V825T
alone. The creep curves of Compositions 1 and 2 prove that this
effect is not due to the HT121; on the contrary, the latter
ungrafted polymer results in a deterioration in the stress cracking
resistance properties.
* * * * *